There are NO MORE older, compatible apps available for download/install from the Apple iOS App Store, any longer, for that over 10-year old, 1st, generation iPad.
None!
It’s time for a new, new, refurbished or much “newer” or newer, used iPad model.
A WHOLE LOT has happened with iPad/iOS in over 10-years!
If you must purchase older, used iPad models, DO NOT look at anything older than a 2014 iPad Air 2 or 2015 iPad Mini 4.
Both of these models are the oldest iPad models that the up and coming iPadOS 14 will support, in the Fall of 2020.
If you must purchased used devices from unknown, untrusted sources, you must ask A WHOLE LOT more questions of the iOS device seller, ask for more photo/images, ask if the iPad has user/iCloud activation lock and ask for photos/images/short video proof, ANY POSITIVE, UNQUESTIONABLE, VISUAL PROOF, that such an iPad has been reset to factory settings and shown proof of the iOS device's start up screen showing the animated, moving, multi-language “Hello” Welcome to iPad screen.
If the iOS device seller is unwilling to do all of this to show you that the iPad, in question, is ready to use with no barriers to new user activation and use, pass on the iOS device and look at other iOS device sellers, elsewhere, who will be more accommodating to answering questions and providing visual image or video proof of a proper factory reset iPad.
Sorry & Best of Luck to You!